A man and a woman were shot dead in their house on Sunday night in Chulabhorn district of this southern province, police said.
Pol Capt Khamnueng Songkwan, duty officer at Chulabhorn police station, said the shooting was reported about 9.30pm.
Police and a doctor were rushed to the house, in Khuan To village of tambon Thung Pho.
Boontham Panarat, 48, and Uma Paenkaew, 48, were found dead in the house. Boontham was shot three times, in the head, and Uma five times, in the head, arm and a leg,
Spent 9mm bullet casings were found at the scene.
Police said Boontham was a widower and Uma a widow. They lived together as husband and wife.
Neighbours told police they heard Boontham and Uma in a heated argument with another person, and then the sound of gunshots.
Police said the killer fled, but they believed the shooter was well known to the victims.